About 20 minutes of vigorous grinding, mostly in a circular motion.
When I was researching on culinary forums, a repeated suggestion was to get a large capacity mortar.
Was a nice little workout for the forearms.
Before the rice grinding, I vigorously scrubbed it with a brush & reverse osmosis water for a good 12 - 15 minutes.
Bought an under-sink reverse osmosis 5-stage water filtration system a year ago & am very happy with the purchase.
It's already paid for itself with the savings from not purchasing 5-gallon jug refills from the store & lugging them home every week.
Will be sure to clean this mortar with r.o. water only, so no funky tap water residues mar my culinary exploits.
Do you have a mortar & pestle?
If so, what are your favorite & most frequent preparations?